1. Field of the Invention
Embodiments of the present invention relate generally to the analysis of earth stresses associated with hydrocarbon recovery and, more particularly, to determining effective displacements and stresses resulting from the injection and/or withdrawal of pressurized fluids.
2. Description of the Related Art
Hydrocarbon recovery processes may occur in subterranean reservoir sands or shales, may employ single or multiple water injection wells, and may be energetic by design. Recovery processes may require large pressure and/or temperature changes to promote the extraction of oil and gas at economic rates from subterranean formations. Water injection wells may be employed in either a secondary water flood strategy to sweep residual oil to production wells and provide pressure support, or strictly to dispose of produced water. The pressure or temperature changes, induced during the injection and/or withdrawal of pressurized fluids, result in stresses to the formation that may lead to some combination of fracturing, expansion and contraction of the subterranean formations.
These fracturing, expansion and contraction processes typically cause excess pore pressure and stress changes within the formations that may be large enough to negatively impact well mechanical integrity, productivity, injectivity and conformance. They may also be large enough to exceed the mechanical limits of penetrating wells. If the mechanical limits are exceeded, some combination of expansion and fracturing of the well or subterranean formation may occur. As a result, the penetrating wells may no longer be capable of sustaining reliable hydrocarbon production safely and without risk to the environment.
Many of the same risks are present in water flood or water disposal campaigns and success may depend on the capabilities to manage early water breakthrough and contain hydrofracture growth within the target subterranean interval(s). For water flooding, the expansion and fracturing process may lead to “short circuiting” of injector-producer patterns and loss of pressure support. For water disposal, these processes may lead to a loss of containment that may result in repressurization of untargeted zones and, potentially, regulatory and environmental consequences.
Prior art methods employed for analysis of earth stresses associated with the injection or production of hydrocarbons have usually adopted one of two approaches. In the first approach, conventional well logging (e.g., gamma ray, density, resistivity, and sonic) analysis techniques are utilized in conjunction with production data to infer changes in earth stresses. In the second approach, earth stresses are determined by analytic models or simulators. Either approach typically assumes steady state conditions and is specific only to a particular set of well performance conditions (e.g., single-valued average pressure, rate, temperature and single-layered formation properties).
These conventional approaches fall short of being generalized to account for multiple subterranean layers and variable, time-dependent well performance. In addition, even though displacement measurements from field surveillance may indicate the presence of multi-well interactions, conventional approaches do not scale very easily to account for these interactions at the field-level. Field surveillance methods may include surveys of ground surface displacements via tilt arrays, remote sensing (e.g., Interferometric Synthetic Aperture Radar (InSAR), Light Detection and Ranging (LiDAR), Global Positioning System (GPS)) or vertical profiling of recorded passive and/or active microseismic (μ-seismic) events. The underlying methodology of the prior art also precludes rapid forward or inverse modeling with field surveillance data to further constrain modeling problems and allow calibration of the model with collected field surveillance data.
The prior art detailing the methods of controlling subterranean injection and hydrocarbon production processes has not focused on multi-well control or the enablement of field-wide control systems. Moreover, the scope of the prior art has been limited to detecting some time-dependent, single-well characteristic of the resident or injected fluids, changes in the geometry of a hydrofracture, or a principal stress change within the very near-well regime for predicting phenomena, such as the potential for or onset of sand production.
Accordingly, what is needed is a well-based and/or a field-based, injection control process that accurately models multi-layered subterranean formations and predicts injection conditions required to improve injector performance while minimizing undesirable fracture growth and the potential for loss of fracture containment.